On the evening of May 23, 2014, several supercell thunderstorms rumbled along the border between North and South Carolina and dropped significant amounts of hail. Much of the hail was quarter-sized, but the strongest storms unloaded chunks of ice as large as baseballs, according to National Weather Service staff in Columbia, South Carolina. As observers on the ground documented the hail pummeling the ground, NASA’s high-flying ER-2 aircraft flew high overhead.

During one flight, pilot Stu Broce took this photograph of the overshooting top of a storm over North Carolina. For perspective, the storm was about 50,000 feet (15,000 meters) tall, while the ER-2 cruised at an altitude of 65,000 feet (20,000 meters). (Commercial airliners usually fly at about 30,000 feet or 9,000 meters.) Overshooting tops are dome-like protrusions at the top of thunderstorms that provide evidence of very strong updrafts. Severe storms tend to have larger and longer-lived overshooting tops than less intense storms.

During the six-week campaign over the southern Appalachian mountains, NASA and partners at Duke University and NOAA’s Hydrometeorological Test Bed set up ground stations with rain gauges and ground radar. They also collected data from satellites and two aircraft. When the ER-2 finally returned to NASA Armstrong Flight Research facility in California, it had flown 18 IPHEx science missions totaling more than 95 flight hours.